1. Field of the Invention
The present invention relates to an imaging device having an image sensor, parts of which are used as phase difference method focus detection elements, and to a control method for the imaging device.
2. Description of the Related Art
An image sensor that also has part thereof functioning as photodiodes for focus detection is known (refer to Japanese patent No. 3592147 (referred to hereafter as patent literature 1)). With the image sensor shown in patent literature 1, each pixel of a region that is utilized for focus detection is divided into two pixels, and these two pixels are subjected to subject light flux that has passed through a pupil exit region (hereafter referred to as “pupil region”) that differs depending on a photographing lens, by means of respective on-chip microlenses. Focus state is then detected based on a phase difference between two images that are represented by two image signals that have passed through the differing pupil regions.
Also, when parts of an image sensor are utilized as focus detection elements, as disclosed in patent literature 1, sections that are made the focus detection element constitute defective pixels, and an image is degraded. Interpolation processing for the element outputs is therefore carried out in order to make up for lack of output of the focus detection elements. However, when light of a subject image having high spatial frequency is received, reduction in image sharpness due to the effects of interpolation are very noticeable. With the imaging device disclosed in Japanese patent laid-open No. 2010-062640 (hereafter referred to as patent literature 2) therefore, signal variation at the periphery of a focus detection element is detected, and a proportion of gain adjustment amount to interpolation correction amount is determined based on the results of this detection.